Recordings of the interior of an examination object can be produced by way of various imaging systems that are able to represent the structures in the interior of the examination object. Computer tomography systems or magnetic resonance systems are typically used for this purpose. For easier identification of specific structures in the interior of an examination object, in many cases contrast media are used and image data records of the region of interest are produced during the spreading of the contrast medium in the examination object at different points in time.
By way of the contrast medium, which spreads, accumulates and dissipates again in or at specific structures in a particular manner, these structures become better distinguishable in the images and pathologies or dysfunctions become visible. In this case, the phase in which the images were recorded is significant, that is to say whether the phase is one in which the contrast medium first spreads into the structure or accumulates therein, or whether the images are generated in a phase in which the contrast medium slowly disappears again, that is to say is dissipated, from the structure. In order to be able to correctly assess the images later, it is important, therefore, to determine the contrast medium phase.
By way of example, in order to better identify tissue changes in human or animal bodies, in particular when searching for tumours or vascular diseases, e.g. embolisms, an intravenous contrast medium is usually injected. The latter passes via the right ventricle into the pulmonary circulation and from there via the left ventricle and the aorta or into the individual organs. If the image data records are generated at a point in time at which the contrast medium is flushed via the aorta or the further arteries into the organs, then this is referred to as the so-called “arterial phase”.
Within an organ, the draining veins are then supplied via the capillary arteries, via which veins the contrast medium is washed out or dissipated again at a specific rate. This later point in time is defined as the “venous phase”. In some organs a distinction can also be made between the normal “venous phase” and a “late venous phase”. In the late venous phase, the residues of the contrast medium are flushed out.
For comparison purposes, an image data record without a contrast medium, that is to say generally prior to the contrast medium introduction, is generally also produced as well. This phase is referred to as the “native phase”.
The control of imaging systems, in particular of large systems such as computer tomographs or magnetic resonance tomographs, is generally effected by way of so-called “scan protocols”, which store all the essential machine parameters and also, in the case of recording sequences or studies, the time intervals between the individual recordings. In other words, the scan protocols contain the individual control parameters required for controlling the imaging system fully automatically in accordance with the scan protocol and for generating the desired image data records from the raw data acquired. In this case, different scan protocols are provided for a wide variety of recordings, that is to say that there are for example scan protocols for different body regions, for different recording methods and also—in the case of a contrast medium examination—for the successive recordings in the different contrast medium phases. In this case, a scan protocol may in particular also comprise a plurality of subprotocols constructed such that recordings in the different contrast medium phases are produced automatically.
The associated parameters can then be written to a header data area of the files containing the image data produced, in so far as the parameters are useful for the later evaluation. In the data standard DICOM (Digital Imaging and Communication in Medicine) used at the present time, the “DICOM files” each contain a “DICOM header” containing the parameters. In this case, the parameter “series description” generally also contains expressions such as “native”, “arterial”, “venous” or “late venous” which indicate the contrast medium phase.
These data originally accepted from the scan protocol can therefore be used, in principle. Unfortunately, however, this information is unreliable since the operators very often generate new scan protocols for new recordings by copying a scan protocol already present for other measurement tasks and then adapting the data of the scan protocol to the new measurement task. However, whether and in what form all of the entries are carefully adapted here is at the arbitrary discretion of the operator. This often has the consequence that in the scan protocols parameters which initially appear insignificant to the operator, such as the “series description”, and which only describe the measurement but do not have an actual control effect are not adapted correctly. Errors can then occur in particular during a later evaluation of the image data using these additional data describing the contrast medium phase during the recording.